Low temperature rheology of polyphosphoric acid (PPA) added bitumen

In the present work a laboratory evaluation of the low-temperature rheological properties of neat and polyphosphoric acid (PPA) modified bitumens by using a Dynamic Mechanical Analyzer (DMA) is presented. Fundamental rheological properties were evaluated in controlled kinematic conditions and the results obtained were compared with traditional procedures such as the Fraass breaking point. The results show that the effect of polyphosphoric acid addition at low temperature is strongly dependent on bitumen composition (i.e. wax and asphaltene content), nevertheless it seems that PPA is able to decrease the glass transition temperature (Tg) and to increase the stiffness, improving the low temperature performance of the modified materials.